The present invention relates to measuring devices and more particularly to induction-type meters for measuring mechanical quantities, which meters are useful for measuring force, torque, vibration, acceleration, displacement, and the like.
Induction-type meters for measuring mechanical quantities are used in technology for converting various displacements caused by controlled parameters into an electric signal suitable for remote control, the meters comprising a converter to convert the controlled parameter into a displacement, a converter to convert the displacement into an electric signal and an electric measuring circuit for shaping a specific signal at the output thereof.
Known in the art are various designs of induction-type and transformer converters to convert displacements into electric signals (having variable sizes of magnetic gap, variable gap area, solenoid-operated, magnetoelastic, and the like), operating at frequencies of up to 1000 Hz.
Such converters for converting displacements into electric signals, as a rule, include a closed-loop magnetic circuit, an exciting coil, measuring coil, and a movable armature connected to the object being displaced.
Their common disadvantage resides in the fact that they feature limited sensitivity and accuracy which is due to the readings thereof being dependent on uncontrollable incontrollable mutual displacements of the coils and the armature, which disadvantage requires the use of guides and requires a higher degree of sophistication of the design. Moreover, they suffer from the appearance of a reverse effect which can be reduced by decreasing the value of output signal, which in turn necessitates the use of involved secondary apparatuses, limits the distance between the displacement converter and the amplifier of the electric measuring circuit and restricts the field of application for the converters.
Also known in the art are induction-type converters for converting displacements into electric signals, also comprising a field coil, a measuring coil, but with a magnetic screen, the coils of these converters being connected into the circuit of high-frequency oscillators and changing their inductivity in response to the displacement of a metal plate (screen) connected to an element adapted to respond to a variation of force, torque, and other controlled parameters.
Such converters for converting displacements into an electric signal make use of an open-loop, magnetic circuit system, which permits the setting of several coils at various required distances relative to each other and the use of variously shaped screens, which features permit a variation in the range of measurements and the slope of the static characteristic of the meters.
However, the above-described converters also have their disadvantages, residing in the presence of considerable effects of uncontrolled transverse displacements of the screen, a low degree of contact between mutually inductive coils which reduces the output signal level, and also in the mutual effect of coils which are not inductively coupled to each other.
In the cases discussed above, the magnetic circuits of converters for converting displacement into electric signals can be embodied in any conventional shape, such as an E-shape, U-shape, cup-shape, and the like.
Also known in the art is an induction-type converter for measuring mechanical quantities, including a converter to convert the controlled parameter into a displacement, a converter to convert the displacement into an electric signal, wherein the first converter features elements adapted to be moved relative to each other in response to a change in the controlled parameter, which elements mount a magnetic circuit with a block of coils coupled to the circuit of self-excited oscillator and a metal screen of the second converter.
Any change of the controlled parameter, for example, force, results in a relative displacement of the coil block and the screen, thus changing in turn the coefficients of mutual inductance of the coils, which leads to the appearance of a resultant voltage across the output of the differential electric measuring circuit (differential transformer).
A disadvantage which is common to all conventional meters for measuring mechanical quantities is a rather involved design resulting from the requirement to provide special devices for protecting the converter for converting the controlled parameter into a displacement from lateral components of the load, and for protecting the converter for converting the displacements into an electric signal from transverse displacements, as well as stiff requirements imposed on the installation of said mechanical quantities meters in the designated place.
Another disadvantage of the above-described meters resides in the difficulties experienced in adjusting and matching the working stroke in response to a preset conversion characteristic or when correcting same in response to environmental effects, or a temporary change of the characteristic.